In general, when a patient has a hypodermic injection, an injection needle is shot at an appropriate portion of the body such as skin and muscle to inject medicine inside the patient. Also, a diabetic uses a lancet to sample a small amount of his or her blood by stinging it on any suitable portions, e.g., at fingertip, for routine measurement of blood sugar. The patient having such an injection needle or lancet pierced into the body, especially children, sometimes suffers unendurable pain or uncomfortableness. Also, a substantial area of cells around the tingled portion may often be damaged, requiring some time to be healed. Therefore, there has been long-felt desire to develop a less invasive injection needle and lancet, minimizing the pain (unpleasantness) experienced by the patient.
In fact, some of injection needles have been proposed with a little pain to the patient. For example, the Japanese Patent Laid-Open Publication JPA 10-57490 explains the primary reason of the patient's pain that the needle tip “catches” the skin or flesh as the injection needle is penetrating. Also, it discloses a hypodermic injection needle with multi-beveled tip geometry so as to reduce the pain.
Patent Document 1: JPA 10-57490
The present inventors has found the reason of the pain more precisely as described below, and made the invention based upon the knowledge. As the injection needle is penetrating into the tissue such as skin and flesh of the patient, a contacting surface between an outer surface of the injection needle and the tissue of the patient is increased so that the frictional force therebetween becomes greater and the peripheral cells adjacent to the injection needle are drawn inside deeply. To this end, the peripheral cells are extremely deformed by the physical stress due to the frictional force, and may often be burst away (collapsed) so that a pain-producing chemical mediator such as histamine and bradykinin is released within the tissue, thereby hurting the patient. Also, the peripheral cells collapsed by the physical stress extend across the substantial region, which makes more painful and less healable. As described above, the conventional injection needle is highly invasive to pierce the tissue of the patient.
Also, the lancet is used to sample a drop of blood by stinging into the tissue at the appropriate portion of the patient's body. Thus, while there are possible drawbacks as the above-mentioned injection needles, it is highly desired to provide the lancet designed less invasive by minimizing the frictional stress to the peripheral tissue of the patient. According to the medical needle of the present invention, it cuts the peripheral cells as few as possible and wedges away the intact tissues into the deep inside, as will be described herein in detail.
Therefore, one of the aspects of the present invention is to provide a less invasive medical needle giving less pain to the patient.